Fix DummyHandlers to authorize and send/validate correct XMLs

[harshavardhana]

Description

Fix DummyHandlers to authorize and send/validate correct XMLs

Motivation and Context

Fix incorrectly implemented handlers

Regression

No

How Has This Been Tested?

Using AWS SDKs

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added unit tests to cover my changes.
• I have added/updated functional tests in mint. (If yes, add mint PR # here: )
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #7223 into master will decrease coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #7223      +/-   ##
==========================================
- Coverage    48.8%   48.78%   -0.03%     
==========================================
  Files         295      295              
  Lines       45512    45515       +3     
==========================================
- Hits        22214    22203      -11     
- Misses      21274    21284      +10     
- Partials     2024     2028       +4

Impacted Files	Coverage Δ
cmd/dummy-handlers.go	0% <0%> (ø)	⬆️
cmd/posix.go	64.52% <0%> (-1.18%)	⬇️
cmd/fs-v1-helpers.go	68.19% <0%> (-0.62%)	⬇️
cmd/posix-list-dir_windows.go	60.29% <0%> (+1.47%)	⬆️
cmd/disk-usage.go	100% <0%> (+5.26%)	⬆️

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[harshavardhana]

Fixed PTAL @kannappanr @ebozduman

[kannappanr]

LGTM

[ebozduman]

LGTM

[minio-ops]

Mint Automation

Test	Result
mint-compression-xl.sh	✔️
mint-xl.sh	✔️
mint-large-bucket.sh	✔️
mint-compression-dist-xl.sh	✔️
mint-compression-fs.sh	✔️
mint-worm.sh	✔️
mint-fs.sh	✔️
mint-dist-xl.sh	✔️
mint-gateway-nas.sh	✔️